Makefile

@@ -102,6 +102,10 @@ fix-includes: all
 stresstest: test
 	./stresstest/stresstest.sh build/tests/simplest_fib_test
 
+PHONY: test-echo
+test-echo:
+	./tools/test-echo-server-and-client
+
 # TODO: Determine how we can run also jobs from the 'test' stage,
 # e.g. test-gcc.
 .PHONY: gitlab-runner

apps/EchoClient.cpp

@@ -18,7 +18,8 @@
 #include <cstring>	// for memcmp
 #include <iomanip>
 #include <iostream>	 // for operator<<, basic_ostream, endl
-#include <string>		 // for allocator, string, char_traits
+#include <ratio>
+#include <string>
 #include <thread>
 #include <utility>
 
@@ -69,6 +70,8 @@ size_t size = SIZE;
 size_t server_backlog = SERVER_BACKLOG;
 bool linked_futures;
 bool histogram = false;
+static ssize_t maxLowLoadClients = -1;
+static std::chrono::milliseconds loadSwitchPeriod(1000);
 
 std::atomic<bool> terminate = false;
 
@@ -225,6 +228,24 @@ class Client {
 		}
 	}
 
+	[[nodiscard]] auto shouldYield() const -> bool {
+		if (maxLowLoadClients < 0) {
+			return false;
+		}
+
+		if (id < static_cast<size_t>(maxLowLoadClients)) {
+			return false;
+		}
+
+		auto now = std::chrono::steady_clock::now();
+		auto now_ms = std::chrono::time_point_cast<std::chrono::milliseconds>(now);
+		auto ms_since_epoch = now_ms.time_since_epoch();
+		auto ms_since_epoch_duration =
+				std::chrono::duration_cast<std::chrono::milliseconds>(ms_since_epoch);
+		uint64_t periodNum = ms_since_epoch_duration / loadSwitchPeriod;
+		return periodNum % 2;
+	}
+
  public:
 	template <bool collectTimeStamps = false>
 	void run() {
@@ -237,6 +258,11 @@ class Client {
 		startSem.acquire();
 
 		while (iteration < iterations && !terminate.load(std::memory_order_relaxed)) {
+			if (shouldYield()) {
+				emper::yield();
+				continue;
+			}
+
 			SendFuture sendFuture(sock, outBuf, size, MSG_NOSIGNAL);
 			RecvFuture recvFuture(sock, inBuf, size, MSG_WAITALL);
 
@@ -361,8 +387,10 @@ static void printUsage(char* name) {
 	std::cerr
 			<< "Usage: " << name
 			<< "[-h] [-p <port>] [-c <clients>] [-a <address>] [-s <size>] [-b <server backlog>]"
-				 " [-f <output-file>]  [-i <iterations> | -t <execution time in sec>] [--linked-futures]"
-			<< std::endl;
+			<< std::endl
+			<< "[-f <output-file>]  [-i <iterations> | -t <execution time in sec>] [--linked-futures]"
+			<< std::endl
+			<< "[--max-low-load-clients <num>] [--load-switch-period-ms <num>]" << std::endl;
 }
 
 auto main(int argc, char* argv[]) -> int {
@@ -446,6 +474,25 @@ auto main(int argc, char* argv[]) -> int {
 		}
 	}
 
+	char* max_low_load_clients = getOption(argc, argv, "--max-low-load-clients");
+	if (max_low_load_clients) {
+		maxLowLoadClients = std::stoi(max_low_load_clients);
+		if (static_cast<size_t>(maxLowLoadClients) >= nclients) {
+			DIE_MSG("--max-low-load-clients " << maxLowLoadClients
+																				<< " must be smaller than the total number of clients "
+																				<< nclients);
+		}
+	}
+
+	char* load_switch_period_ms_string = getOption(argc, argv, "--load-switch-period-ms");
+	if (load_switch_period_ms_string) {
+		if (!max_low_load_clients) {
+			DIE_MSG("Can't use --load-switch-period-ms without --max-low-load-clients");
+		}
+		int load_switch_period_ms = std::stoi(load_switch_period_ms_string);
+		loadSwitchPeriod = std::chrono::milliseconds(load_switch_period_ms);
+	}
+
 	int err = getaddrinfo(host.c_str(), port.c_str(), nullptr, &server);
 	if (err) {
 		if (err == EAI_SYSTEM) {

apps/EchoServer.cpp

@@ -63,6 +63,7 @@ auto main(int argc, char* argv[]) -> int {
 
 			if (unlikely(bytes_recv == 5 && strncmp("quit\n", buf, bytes_recv) == 0)) {
 				quit = true;
+				std::cout << "Echoserver received 'quit' command from client" << std::endl;
 				Runtime::getRuntime()->initiateTermination();
 				break;
 			}

tools/test-echo-server-and-client

+#!/usr/bin/env bash
+# SPDX-License-Identifier: LGPL-3.0-or-later
+# Copyright © 2021 Florian Schmaus
+set -euo pipefail
+
+SCRIPTDIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )"
+ROOTDIR="$(readlink -f "${SCRIPTDIR}/..")"
+BUILDDIR="${ROOTDIR}/build"
+
+echoerr() { echo "$@" 1>&2; }
+
+PRESERVE_TMPDIR=false
+while getopts :dp OPT; do
+	case $OPT in
+		d)
+			PRESERVE_TMPDIR=true
+			set -x
+			;;
+		p)
+			PRESERVE_TMPDIR=true
+			;;
+		*)
+			print "usage: ${0##*/} [-d] [--] ARGS..."
+			exit 2
+	esac
+done
+shift $(( OPTIND - 1 ))
+OPTIND=1
+
+if [[ ! -L "${BUILDDIR}" ]]; then
+	make -C "${ROOTDIR}"
+fi
+
+TMPDIR=$(mktemp --directory --tmpdir=/var/tmp emper-echo-test.XXXX)
+cleanup() {
+	if ! $PRESERVE_TMPDIR; then
+		rm -rf "${TMPDIR}"
+	fi
+
+	# Ensure that we don't leave a stray echoserver
+	if pgrep --count echoserver > /dev/null; then
+		killall echoserver
+	fi
+}
+trap cleanup EXIT
+
+echo "Starting echo client/server test. Using ${TMPDIR} for logs"
+
+readonly ECHO_CLIENT="${BUILDDIR}/apps/echoclient"
+readonly ECHO_SERVER="${BUILDDIR}/apps/echoserver"
+
+run_echo_client_and_server() {
+	local -r run_name="${1}"
+	local -r echo_client_opts="${2-}"
+
+	local -r logdir="${TMPDIR}/${run_name}"
+	mkdir "${logdir}"
+
+	local -r echo_server_pidfile="${logdir}/echo_server.pid"
+
+	echo "Performing echo client/server ${run_name} run. Logdir: ${logdir}"
+
+	"${ECHO_SERVER}" \
+		> "${logdir}/server.log" \
+		2> "${logdir}/server.err" &
+	echo "${!}" >> "${echo_server_pidfile}"
+
+	# Wait till the echo server port becomes accessible.
+	# https://stackoverflow.com/a/50055449/194894
+	timeout 30 bash -c \
+		'until printf "" 2>>/dev/null >>/dev/tcp/${0}/${1}; do sleep 1; done' \
+		localhost 12345
+
+	set +e
+	# shellcheck disable=SC2086
+	"${ECHO_CLIENT}" \
+		 ${echo_client_opts} \
+		 > "${logdir}/client.log" \
+		 2> "${logdir}/client.err"
+	local echo_client_ret="${?}"
+	set -e
+
+	local echo_server_pid
+	echo_server_pid=$(cat "${echo_server_pidfile}")
+	if ps -p "${echo_server_pid}" > /dev/null; then
+		# TODO: Re-enable this warning once the client is sending a
+		# 'quit' once it is finished.
+#		echoerr "WARNING: echo server was not terminated by client"
+		kill "${echo_server_pid}"
+	fi
+
+	if [[ "${echo_client_ret}" -ne 0 ]]; then
+		echoerr "ERROR: Echo client exited with ${echo_client_ret}"
+		PRESERVE_TMPDIR=true
+		exit 1
+	fi
+}
+
+run_echo_client_and_server "quicktest" "-c 10 -i 10"
+
+run_echo_client_and_server "load-switch" "-c 100 -i 1000 --max-low-load-clients 50 --load-switch-period-ms 250"